1. Field of the Invention
The present invention relates to traffic signal control apparatuses, particularly a traffic signal control apparatus that can handle off-peak traffic up to over-heavy traffic by predicting change in the traffic status from the present to the future to optimize the signal control parameter by the rolling horizon scheme up to the status of near-saturation and executing politic control in the status of over-saturation.
2. Description of the Background Art
Conventional traffic signal control apparatuses are known that calculate the signal control parameter (cycle, split, offset) by a central device to control signal terminals.
When there is a sudden change in the traffic status, the timing of altering the signal control parameters is delayed in the conventional traffic signal control apparatus. There are cases where a great jam in traffic occurs.
An object of the present invention is to provide a traffic signal control apparatus that can correspond to a sudden change in the traffic status.
According to an aspect of the present invention, a traffic signal control apparatus includes a collector unit collecting traffic information through a sensor provided at the road, and an optimization unit predicting change in the traffic status from the present to the future and optimizing the signal control parameter by the rolling horizon scheme. The collecting cycle of traffic information and the optimization cycle can be defined independently. The optimization cycle can be made variable according to the cycle of signal control or the traffic status.
According to the present invention, the rolling horizon scheme is employed. Since the traffic information collecting cycle and optimization cycle can be defined independently, and since the optimization cycle according to the signal control cycle or the traffic status is set variable, a traffic signal control apparatus that can correspond to sudden change in traffic status can be provided.
Preferably, the traffic signal control apparatus carries out optimization of a signal control parameter individually for each street intersection while maintaining the integrity of the entire network by exchanging the traffic information and signal control contents between adjacent street intersections.
By exchanging the traffic information and signal control contents between adjacent street intersections, a traffic signal control apparatus more adaptable to practical usage can be provided.
Preferably, the traffic signal control apparatus further includes a unit predicting the tiring of a vehicle from the present to future traffic volume arriving at the stop line using a traffic flow measurement unit installed upstream a link and expected flow-in traffic volume obtained from an upstream street intersection.
By predicting the timing of a vehicle from the present to future traffic volume arriving at the stop line using the expected flow-in traffic volume, a traffic signal control apparatus of better control can be provided.
Preferably, the traffic signal control apparatus has the function to realize signal control taking into consideration individually or simultaneously reduction of the risk of a traffic accident, influence to the environment, and reducing the number of stops of a bus and other public transportation at a traffic signal.
By realizing signal control taking into consideration the risk of a traffic accident and the like, a traffic signal control apparatus that can provide better control of the traffic signal can be provided.
Preferably, the traffic signal control apparatus has the self correction function to correct the estimated expected flow-out amount by the relationship between the history of the traffic signal light color and the traffic volume measured by the traffic flow measurement device of the flow-out destination link.
According to the present invention, a traffic signal control apparatus that can correct the estimated expected flow-out amount can be provided.
Preferably, the traffic signal control apparatus has the-function to correct the estimated traffic jam length according to the traffic jam length measured by an image sensor or the traffic jam length calculated from traffic information obtained from a traffic flow measurement device.
According to the present invention, a traffic signal control apparatus that can correct the estimated traffic jam length can be provided.
Preferably, the traffic signal control apparatus has the function to alter the weight coefficient of each cost element of the evaluation function of the signal control parameter according to the traffic status, region characteristics and control target.
According to the present invention, a traffic signal control apparatus that can alter the weight coefficient of each cost element of the evaluation function of a signal control parameter can be provided.
Preferably, the traffic signal control apparatus has the function to switch the control target from cost minimization to handling amount maximization, or to switch to priority control giving a particular direction priority when vehicles of a traffic demand exceeding the street intersection processing ability flows to the intersection.
According to the present invention, a traffic signal control apparatus that can switch the control target according to the status can be provided.
Preferably, when excessive traffic jam occurs locally at some links, the traffic signal control apparatus has the function to expedite the processing amount of these links by alleviating the blue traffic light time maximum restriction and setting the weight coefficient of a downstream delay which is one cost element to zero.
According to the present invention, a traffic signal control apparatus can be provided capable of facilitating the processing amount of a link when local excessive traffic jam occurs.
Preferably, the traffic signal control apparatus includes a unit switching the signal control method according to each traffic status of nonsaturation, near-saturation and over-saturation, in an abnormal status, or in response to an instruction.
According to the present invention, a traffic signal control apparatus that can switch the signal control method according to the traffic status, an abnormal status, or in response to an instruction can be provided.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.